As low-dimensional nano-materials consisting of carbon atoms, there are fullerene, a carbon nanotube, graphene, graphite, and the like. That is, if carbon atoms are arranged in a hexagonal shape to form a ball shape, fullerene having a zero (0)-dimensional structure is obtained. If carbon atoms are one-dimensionally rolled, a carbon nanotube is obtained. If carbon atoms form one two-dimensional atom layer, graphene is obtained. If carbon atoms are three-dimensionally stacked, graphite is obtained.
Particularly, electrical, mechanical, and chemical characteristics of graphene are highly stable and excellent. The graphene is a highly conductive material, which can move electrons 100 times faster than silicon and enable flow of about 100 times more currents than copper. The characteristics of the graphene have been verified through experiments since discovery of a method of isolating the graphene from graphite in 2004. Since then, a great deal of research on this matter has been carried out.
Since the graphene is composed of only carbons, which are relatively light atoms, it facilitates processing of a one- or two-dimensional nanopattern. By using the graphene, semiconductive-conductive properties can be adjusted. By using diversity of chemical bonds of carbons, wide-range functional devices such as sensors and memories can be fabricated.
However, due to lack of a method for effective synthesis, transfer, and doping, quality and a scale required to actually produce a graphene film have been restricted. For example, a conventional transparent electrode, such as an indium tin oxide (ITO), which is generally used for a solar cell, exhibits unlimited scalability, ˜90% of optical transparency, and a sheet resistance smaller than 100 Ohm/square. However, the highest records of the graphene film still remain about ˜500 Ohm/square of sheet resistance, ˜90% of transparency, and a scale of several centimeters.
In order to solve the problems, the present disclosure provides a roll-to-roll doping method of a graphene film, which includes doping the graphene film by immersing the graphene film in a doping solution containing a dopant and passing the graphene film through the solution, or passing the graphene film through a dopant vapor generated by vaporizing the doping solution by using a roll-to-roll process, a graphene film doped by the method, and a roll-to-roll doping apparatus of a graphene film.
However, problems sought to be solved by the present disclosure are not limited to the above-described problems. Other problems to be solved by the present disclosure, which are not described herein, can be clearly understood by those skilled in the art from the descriptions below.